Conventionally, there has been known a car navigation system equipped with a character string arrangement function of arranging a character string such as a road name along a road line (hereinafter referred to as a “road node sequence”) from a node for starting an arrangement of the character string (hereinafter referred to as an “arrangement start node”) (for example, see Patent Document 1 to Patent Document 3). When the character string arrangement function is used, characters are arranged in parallel with the road; thus, when a character string extending over two links is arranged, a change in angle between road links (hereinafter referred to as a “road angular change”) becomes equal to a change in arrangement angle between characters (hereinafter referred to as a “character angular change”).